Method and apparatus for forming blasting holes in rock



March 13, 1956 R. B. AITCHISON 2,738,162

ETHOD AND APPARATUS FOR FORMING BLASTING HOLES IN ROCK Filed Feb. 27,1953 2 Sheets-Sheet l Z7 INVENTOR ROBBYERT B AITCHISON ATTORNEY March13, 1956 R. B. AITCHISON METHOD AND APPARATUS FOR FORMING BLASTING HOLESIN ROCK Filed Feb. 27, 1953 2'Sheets-Sheet 2 INVENTOR ROBERT B.AITCHISON ATTORNEY procedure.

METHOD AND APPARATUS FOR FORMING BLASTING HOLES IN ROCK Robert B.Aitchison, Jackson Heights, N. Y., assignor to Union Carbide and CarbonCorporation, a corporation of New York Application February 27, 1953,Serial No. 339,301

11 Claims. (Cl. 255-13) The present invention relates to a novel methodand apparatus for forming blasting holes in rock. More particularly, itconcerns such a method and apparatus for thermally enlarging a bore ina'body of rock. The invention can be used successfully on such rocks asquartzite, dolomite, trap-rock, the low-grade iron ore known astaconite, and others.

Deep blasting holes have been bored successfully in rock bodies by theflame piercing method and apparatus described in United States ReissuePatent Re. 22,964, granted January 20, 1948, to C. J. Burch. Mechanicaldevices such as churn drills also have been .used, particularly on thesofter rocks. As the diameter of the holes desired has increased, largerand heavier equip ment and more powerhave been required to operate it.For example, the flame piercing of blasting holes having a minimumdiameter of 6% inch and a depth of 30 feet in taconite iron ore hasrequired a blowpipehaving a diameter of 4% inches and weighing about aton; and the direct piercing of holes having a larger diameter wouldrequire an even larger and heavier blowpipe.

Naturally the amount of explosive which can be loaded into a hole orsmall diameter is strictly limited. Heretofore it has been customary tospring the bottom portion of such a small hole by repeatedly explodingsmall charges of explosive at the bottom and clearing out the detritusto form an enlarged chamber for receiving the final charge of explosive.This procedure is slow, laborious, uncertain, dangerous, and expensive;and is limited to forming a chamber at the bottom of a bore.

Among the objects of the present invention are to produce thermally inrock a blasting hole having at least a portion of larger diameter thancould be obtained efficiently by direct flame piercing with equipment ofthe same size, weight, and power; and to increase thermally over all orany part of its length the diameter of a blasting hole previously formedin rock by any known Other objects are to provide novel 'apparatus forthermally enlarging a blasting hole'over all or any part of its length;and to provide such apparatus which operates to increase the diameter ofa blasting hole beyond that which can be efficiently obtained directlyby flame piercing equipment of the same size, weight, and power.

The above and other objects will become apparent from the followingdescription, having referenceto the annexed drawings, wherein:

Fig. l is a schematic side elevational view, partly in section, showingapparatus including a blowpipe for thermally increasing the diameter ofa blasting hole in accordance with the invention;

Fig. 2 is an enlarged longitudinal sectional view of the lower end ofthe blowpipe shown in Fig.1;

Fig. 3 is sectional view taken along the line 3-3 in Fig. 2;

Fig. 4 is a longitudinal sectional view through the lower end of ablowpipe which can be used for directly piercing a blasting hole in abody of rock;

A United States Patent fiice 2,738,1fl2 Patented Mar. 13, 1956 Fig. 5 isa schematic view showing the lower portion of a blowpipe when enlarginga bore in a single pass;

Fig. 6 is a sectional view of the lower end of a modified blowpipeembodying the present invention; and

Fig. 7 is a schematic view showing the lower portion of the blowpipe ofFig. 6 when enlarging a bore in a single pass.

' In accordance with the present invention there is provided a novelmethod for increasing the diameter of a blasting hole or bore in a bodyof rock by directing a high (supersonic) velocity flame jet having aradial component against a peripheral zone of the side wall of the boreto loosen and remove material therefrom, and traversing the highvelocity flame jet in a direction axially of the bore to remove materialor detritus from successive peripheral zones of the side wall. Thedetritus is promptly and continuously cleared from the bore, as byejection with a flowing stream of ejection fluid. The high velocityflame jet removes material predominantly by spalling it oif as unfusedparticles, but in some rocks there is also some melting; e. g. inquartzite the material is removed almost entirely by spalling, whereasin taconite iron ore there is noticeable melting. Other rocks melt moreor less than taconite.

In the embodiment of the invention shown in Figs. 1-5 of the drawings,the high veloctiy flame jet is provided as one or more individual radialflame jets which are rotated around the longitudinal axis of the bore sothat they impinge against a peripheral zone of the side wall. Thus, eachflame jet follows a helical path. as it traverses the bore axially.Additionally, as the flame removes material, jets of water are injectedinto the bore adjacent the flame jet to quench the hot material andsolidify any molten part, and this water flashes to steam when heated bythe flame and the hot detritus. The steam joins with the gaseousproducts of flame combustion to form the ejection fluid for blowingdetritus out of the bore so promptly that there is no time for detritusto accumulate and melt. Furthermore, since some quite large particles ofmaterial are spalled oif by the high velocity flame jet or are formedwhen molten material is quenched, it has been found advantageous tomechanically disintegrate such particles in the bore to permit theirejection.

It has been found that rock formations which cannot be effectivelyspalled by conventional low velocity flames, such as granite whichcontains many high melting point constituents, are easily spalled andsprung in accordance with the present invention. This is believed to beattributable to the fact that the high (supersonic) velocity flame jetsemployed in the present invention are capable of delivering heat at ahigher transfer rate and are accompanied by a mechanical force whichaids in disintegrating the rock formation to which the flame jet isapplied. In addition, spalling, being a thermal surface effect, does notrequire deep heat penetration such as is accomplished through the use oflow velocity flames. Thus, the action of the high velocity jet is moreeflicient in thermally spalling formations which cannot be effectivelyspalled by the action of a conventional low velocity, heat soaking typeof flame. Referring to Fig. 1 of the drawings, there is shown anelongated blowpipe 11 which is suspended within a vertical bore 13 in abody of rock 14 by a cable 15 passing over a pair of sheaves 17 and 19on the top of a vertical mast 21 which is mounted on a mobile platform23. Cable 15 is wound on a drum 25, also mounted on platform 23, forraising and lowering the blowpipe.

Blowpipe 11 has a nozzle 27 at its front end provided with a pair ofoppositely disposed radial flame jet ports 29 and 31 (Figs. 2 and 3)having their axes at right angles to the longitudinal axis of theblowpipe for directing a pair of horizontal high velocity flame jetsradially against the side wall 33 of the bore. A burning combustiblefluid, such as a mixture of oxygen and kerosene, enters ports 29 and 31from an internal combustion chamber 32 which is supplied with oxygen andkerosene by passage 34 and injector 36, respectively.

The high velocity flame jets from ports 29 and 31 are rotated around thelongitudinal axis of the bore 13 by rotating the whole blowpipe 11 bymeans of a mechanism 35 operated by a gear reducer and electric motorset 37 controlled by start and stop switches and 41. Mechanism 35 may beof any suitable type, such as that described in United States Patent2,338,093, issued January 4, 1944, to W. T. Caldwell. The rotatingmechanism there described is constructed with keys sliding inlongitudinal grooves such as the groove 38 on the blowpipe, so that theblowpipe can be rotated and also moved longitudinally up or downsimultaneously.

Longitudinal movement of the blowpipe up or down is accomplished by thedrum 25 which is operated by a gear reducer 39 and electric motor 42controlled by electrical switches 43, 44 and 45. When the operatorwishes to raise the blowpipe in the hole he presses the switch 43 whichcauses the motor 42 to rotate the drum 25 counterclockwise to wind upcable 15. When the operator wishes to lower the blowpipe in the hole hepresses the stop switch 44 and then the switch 45 which reverses therotation of motor 42 and causes drum 25 to rotate clockwise and pay outcable.

Sometimes the diameter of an approximately cylindrical bore 13 is to beenlarged locally to form an approximately cylindrical chamber 48 forreceiving a larger quantity of explosive than otherwise could be loaded.Then the blowpipe 11 is lowered into the bore 13 with the high velocityflame jets burning until the nozzle 27 is at the bottom of the desiredchamber, and rotation of the blowpipe is begun to cause the radial flamejets from ports 29 and 31 to impinge against the side wall 33. At thesame time or shortly thereafter the operator starts the drum motor 42 tocause the blowpipe to be raised slowly. The radial high velocity flamejets thus impinge against successive peripheral zones and removematerial for enlarging the diameter of the bore. When the nozzle 27 hasreached the top of the desired chamber the operator then reverses thedrum motor 42 and lowers the blowpipe slowly to enlarge the diameterstill more. This back-and-forth movement of the blowpipe is continuedfor any number of cycles, as experience may dictate, until the desiredenlargement has taken place. Obviously if the nozzle 27 is firstpositioned at the top of the desired chamber, the first step is to lowerthe nozzle slowly to its bottom. The size of the chamber can becontrolled much more effectively than in the previous procedure ofexploding successive small explosive charges to spring the hole.

During the operation of the blowpipe 11 cooling water is supplied to anannular chamber in the nozzle 27 and jets of this water are dischargedradially from a plurality of circumferentially arranged ports 46 in thenozzle slightly to the rear of the flame ports 23 and 31. A single jetof water also is discharged axially through an axial port 46a. Thesejets of water are vaporized to steam by the heat of the high velocityflame jet and by contact with the hot detritus, and the steam cooperateswith the gaseous products of flame combustion to eject detritus from thebore.

Since some of the material removed from the side wall of the bore may beoverly large for ejection, four or more radially extending longitudinalteeth 47 are provided on a removable sleeve near the front end ofblowpipe 11 just to the rear of water ports 46 so as to rotate with theblowpipe and disintegrate such large particles. Water from ports 46cools the teeth 47 to protect, them from deterioration by the heat.

The bore 13 shown in Fig. 1 has been locally enlarged tained by fullyloading such a hole.

at the bottom providing a large chamber 48 to receive an explosive. Oneor more similar chambers can be formed any where along the length of abore singly or as a series separated from one another by portions of thebore having the original diameter. Charging an explosive charge into achamber located near the top of a blasting hole causes greaterfragmentation than heretofore, which reduces the amount of secondarypiercing and blasting necessary.

It is also frequently desirable to enlarge the diameter of a bore overits entire length by generally following the procedure described above,by extending the back-andforth traversing movement of the blowpipe overthe entire bore. The maximum explosive effect can be ob- Such procedureis of particular importance where the explosive charge to be used iscontained in an inflexible metallic cannister.

A predetermined minimum bore enlargement can be obtained in a singlepass by starting at the top and lowering the blowpipe slowly into thebore. In this case the over-all diameter of the blowpipe teeth should beabout the same as the desired minimum hole diameter, so that theteeth'will hang up on any undersize protuberances in the bore until theyare removed by the high velocity flame jet and the blowpipe can drop tothe next protuberant zone, as shown in Fig. 5. All or any part of thelength of the bore can be enlarged in this way.

The nozzle 27 has been shown in Figs. 1-5 with radial high velocityflame jets having their axes at right angles to the longitudinal axis ofthe blowpipe and the bore, but successful operation has been achievedwhen these radial high velocity flame jets are directed upwardly ordownwardly at a small angle to the blowpipe axis. In fact, a slightupward, or swept back, inclination of the flame jets assists in ejectingdetritus from the bore. A blowpipe having such upward inclination offlame jets is shown in Figs. 67 of the drawings. As there shown,elements have been assigned primed numerals corresponding to thenumerals of equivalent elements of the apparatus shown in Figs. 1-5.Furthermore, while two radial flame jets have been shown by way ofillustration, successful operation has been achieved with a singleradial port; and more than two flame jets also can be used successfully.

While the original bore which is enlarged by the method of the inventionmay be produced in any desired way, as by mechanical drilling or byflame piercing, the present method has been found particularly valuablewhen used in conjunction with a flame piercing procedure. In flamepiercing the bore the same blowpipe 11 is used but, instead of thenozzle 27 having radial high velocity flame jets, the blowpipe isprovided with a nozzle 49 (see Fig. 4) having a longitudinal flame jet51 arranged to impinge an intensely hot high velocity flame jet on thebody of rock in the direction of piercing. This flame jet first producesa shallow depression in the rock which rapidly deepens to form a bore.The blowpipe is advanced into the bore as it deepens to remove morematerial until a bore of a desired depth, such as 30 feet, has beenobtained. During its advance the blowpipe is rotated and is lowereddownwardly in the manner described for enlarging the hole diameter.

The detritus which is loosened from the rock body is ejected from thebore by the gaseous products of combustion and the steam fromevaporating water jets which are injected into the bore from ports 53.Any overly large particles are disintegrated by the rotating teeth 47.When a bore has been completed the blowpipe 11 is withdrawn, and nozzle49 is removed from the blowpipe and replaced by a nozzle 27 havingradial or swept back flame jet, ports, as shown in Figs. 2 and 6. Thenthe lighted blowpipe is re-inserted in the bore and. the diameter isincreased in the manner previously described. Of course, when, the bore.is. to be enlarged by a single downward pass, the sleeve 50 also shouldbe replaced by a sleeve SShaving teeth 57 thereon of about the samover-all diameter as desired in the final hole.

The method and apparatus of the invention have been used successfully inhard taconite iron ore which had been flame pierced originally ;withbores having a depth of 30 feet, and a minimum diameter of 6% inches.One hole was enlarged over its entire lengfli in a single downward passto a minimum diameter of 7 /2 inches at a rate of 60 linear feet perhour. Another hole-was enlarged to a minimum diameter of 8 /2 inchesoyer'its entire length in a single downward pass at a rate of 30 linearfeet per hour. Still another'hole was cnlarged to a minimum diameter of9% inches over its entire length in a single downward pass at a rate of22 /2 linear feet per hour. Enlargement was accomplished with the sameequipment as had been used for the original flame piercing of the bores,except for the substitution of a two-flame jet nozzle of the generaltype shown in Figs. 2, 3, 6 and 7 for the nozzle of the general typeshown in Fig. 4. Oxy-kerosene high velocity flame jets were used.

In other examples of how the method of the invention has been performed,three bores were flame pierced in a body of traprock and were thenenlarged in the manner described above, using a blowpipe nozzle having asingle radial high velocity flame jet in place of the piercing nozzle.One hole having a minimum diameter of 3 /2 inches was enlarged over a 13/2 inch length to a minimum diameter of 6 inches by traversing anoxykerosene flame jet back and forth for 10 cycles at a rate of 18inches per minute while rotating at 20 revolutions per minute. Anotherhole having a minimum diameter of 5 inches was similarly enlarged to aminimum diameter of 6 inches over a 14 /2 inch length in cycles. Stillanother hole having a minimum diameter of 4 inches was similarlyenlarged to a minimum diameter of 7 inches over an 8-inch length in 7cycles.

It is to be understood that in the forming and enlarging of bores by themethod of the invention, natural rock, such as iron ore, is often soformed that an absolutely uniform diameter cannot be obtained by a flameprocess. This is true both in the piercing and the enlarging of a bore.

It is also to be understood that the method of the invention can beperformed on bores extending in directions other than vertically down,for example on horizontal bores. Apparatus of the general type disclosedin the aforementioned U. S. reissue patent Re. 22,964 can then be usedfor manipulating the blowpipe.

Further, it is to be understood that by the words high velocity jet ofburning gases, high velocity flame jet, and flame jet, as employedherein, is meant a flame having a linear velocity exceeding the velocityof sound in the combustible mixture (approximately 3000 linear feet persecond) at thattemperature and pressure. Tests have indicated that flamevelocities of about 4000-5000 linear feet per second are obtainable withthe apparatus of the present invention.

This is a continuation-in-part of my copending application Serial No.188,508, now abandoned.

What is claimed is:

1. The method for increasing the diameter of a bore in a body of rockwhich comprises directing from an internal combustion burner against aperipheral zone of the side wall of said bore a jet of burning gaseshaving a linear velocity greater than sonic velocity, the axis of saidjet forming, in the region between said jet and the open end of saidbore, an angle of less than 90 degrees with the longitudinal axis ofsaid bore; traversing said jet axially of said bore to remove materialfrom successive peripheral zones of said side wall; and ejecting saidmaterial from said bore at least in part by the action of said jet.

2. The method for increasing the diameter of a bore in a body of rockwhich comprises directing from an internal combustion burner against aperipheral zone of the side wall of said bore a jet of burning gaseshaving a linear velocity greater than sonic velocity, the axis of saidjet forming, in the region between said jet and the open end of saidbore,-an angle of less than degrees with the longitudinal axis of saidbore; rotating said jet around the longitudinal axis of said bore toremove material from a peripheral zone of said side wall; and ejectingsaid material from said bore at least in part by the action of said jet.

3. The method for increasing the diameter of a bore in a body of rockwhich comprises directing from an internal. combustion burner against aperipheral zone of the side wall of said bore a jet of burning gaseshaving a linear velocity greater than sonic velocity, the axis of saidjet forming, in theregion between said jet and the open end of saidbore, an angle of less than 90 degrees with the longitudinal axis ofsaid bore; rotating said jet around the longitudinal axis of said boreto impinge said flame jet against a peripheral zone of said side wall;traversing said rotating flame jet back and forth axially of said boreto remove material from successive peripheral zones of said side wall;and ejecting said material from said bore at least in part by the actionof said jet.

4. The method in accordance with claim 3, wherein said rotating flamejet is traversed back and forth along substantially the full length ofsaid bore.

5. The method in accordance with claim 3, wherein said rotating flamejet is traversed back and forth along a portion of the length of saidbore to form an enlarged chamber therein.

6. The method in accordance with claim 3, wherein said rotating flamejet is traversed along a plurality of axially-spaced portions of thelength of said bore to form a series of enlarged chambers thereinseparated from one another by portions of said bore having substantiallythe original diameter thereof.

7. A blowpipe for removing rock comprising an enlarged tubular memberincluding a nozzle at the front end thereof, said nozzle having aninternal combustion chamber, at least one radial flame jet port meansfor providing a flame jet of supersonic velocity and a diverging passagebetween said internal combustion chamber and each of said flame jetports, wherein the axis of said flame jet port means is positioned so asto discharge flame jets having a rearward directional component formingan acute angle with the longitudinal axis of said nozzle; and means forsupplying combustible fluid to said internal combustion chamber.

8. A blowpipe for removing rock comprising an enlarged tubular memberincluding a nozzle at the front end thereof, said nozzle having aninternal combustion chamber, at least one radial flame jet port meansfor providing a flame jet of supersonic velocity, and a diverg ingpassage between said internal combustion chamber and each of said flamejet ports, wherein the axis of said flame jet port means is positionedso as to discharge flame jets having a rearward directional componentform ing an acute angle with the longitudinal axis of said nozzle; meansfor supplying combustible fluid to said internal combustion chamber; andsaid tubular member having a plurality of circumferentially-arrangedports positioned near said front end and to the rear of said flame jetport means for discharging jets of water.

9. A blowpipe in accordance with claim 8, which also comprises radiallyextending teeth secured thereon near said front end in position forbreaking up large particles of rock loosened by said flame jet.

10. Apparatus for thermally increasing the diameter of a bore in a bodyof rock comprising an elongated blowpipe adapted to be inserted in saidbore, said blowpipe having a nozzle at the front end thereof providedwith an internal combustion chamber, at least one flame jet port meansfor directing a flame jet of supersonic velocity against the side wallof said bore to remove material therefrom and a diverging passagecommunicating between said internal combustion chamber and each of saidflame jet port means, the axis of said flame jet port means beingpositioned so as to discharge flame jets having a rearward directionalcomponent formingv an acute angle with the longitudinal axis of saidnozzle; said blowpipe also having radially extending teeth securedthereon near said front end in position to break up large particles ofsaid removed material; means for rotating said nozzle and said teeth toimpinge said flame jet against a peripheral zone of said side wall tocause said teeth to break up said large particles; and means fortraversing said blowpipe back and forth longitudinally thereof toimpinge said supersonic velocity flame jet against successive peripheralzones of said side wall.

11. Apparatus in accordance with claim 10, wherein said blowpipe isadditionally provided with ports positioned near the front end of saidnozzle for discharging water into said bore adjacent said flame jet.

Refesences Cited in the file of this patent UNITED STATES PATENTS2.195,384 Zobel et a1 Mar. 26, 1940 2,286,782 Aitchison Tune 16, I9422,327,482 Aitchison et a1. Aug. 24, 1943 2,327,496 Burch Aug. 24, 19432327,492 Burch Aug. 24, 1943 2,367,119 Hess Jan. 9, 1945 2,628,817Wyland, J'r. Feb. 17, 1953 2,675,993 Smith et a1. Apr. 20, 1954

1. THE METHOD FOR INCREASING THE DIAMETER OF A BORE IN A BODY OF ROCKWHICH COMPRISES DIRECTING FROM AN INTERNAL COMBUSTION BURNER AGAINST APERIPHERAL ZONE OF THE SIDE WALL OF SAID BORE A JET OF BURINING GASESHAVING A LINEAR VELOCITY GREATER THAN SONIC VELOCITY, THE AXIS OF SAIDJET FORMING, IN THE REGION BETWEEN SAID JET AND THE OPEN END OF SAIDBORE, AND AN ANGLE OF LESS THAN 90 DEGREES WITH THE LONGITUDINAL AXIS OFSAID BORE; TRAVERSING SAID JET AXIALLY OF SAID BORE TO REMOVE MATERIALFROM SUCCESSIVE PERIPHERAL ZONES OF SAID SIDE WALL; AND EJECTING SAIDMATERIAL FROM SAID BORE AT LEAST IN PART BY THE ACTION OF SAID JET.